could weaken
Verbo regular: weaken - weakened- weakened

Afirmação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
I could weaken
you could weaken
she could weaken
we could weaken
you could weaken
they could weaken 	I could be weakening
you could be weakening
she could be weakening
we could be weakening
you could be weakening
they could be weakening	I could have weakened
you could have weakened
she could have weakened
we could have weakened
you could have weakened
they could have weakened	I could have been weakening
you could have been weakening
she could have been weakening
we could have been weakening
you could have been weakening
they could have been weakening	

Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
I couldn't weaken
you couldn't weaken
she couldn't weaken
we couldn't weaken
you couldn't weaken
they couldn't weaken 	I couldn't be weakening
you couldn't be weakening
she couldn't be weakening
we couldn't be weakening
you couldn't be weakening
they couldn't be weakening	I couldn't have weakened
you couldn't have weakened
she couldn't have weakened
we couldn't have weakened
you couldn't have weakened
they couldn't have weakened	I couldn't have been weakening
you couldn't have been weakening
she couldn't have been weakening
we couldn't have been weakening
you couldn't have been weakening
they couldn't have been weakening	

Forma interrogativa 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
could I weaken?
could you weaken?
could she weaken?
could we weaken?
could you weaken?
could they weaken? 	could I be weakening?
could you be weakening?
could she be weakening?
could we be weakening?
could you be weakening?
could they be weakening? 	could I have weakened?
could you have weakened?
could she have weakened?
could we have weakened?
could you have weakened?
could they have weakened? 	could I have been weakening?
could you have been weakening?
could she have been weakening?
could we have been weakening?
could you have been weakening?
could they have been weakening? 	

Forma interro-Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
couldn't I weaken?
couldn't you weaken?
couldn't she weaken?
couldn't we weaken?
couldn't you weaken?
couldn't they weaken? 	couldn't I be weakening?
couldn't you be weakening?
couldn't she be weakening?
couldn't we be weakening?
couldn't you be weakening?
couldn't they be weakening? 	couldn't I have weakened?
couldn't you have weakened?
couldn't she have weakened?
couldn't we have weakened?
couldn't you have weakened?
couldn't they have weakened? 	couldn't I have been weakening?
couldn't you have been weakening?
couldn't she have been weakening?
couldn't we have been weakening?
couldn't you have been weakening?
couldn't they have been weakening?